1. Field of the Invention
The present invention relates to a wire printing head for a stylus or wire printer, and in particular, to an armature therefor and a mechanism for driving the armature.
2. Description of the Prior Art
Conventionally, various types of printing heads including plunger type and clapper type printing heads, have been employed in stylus printers. In order to provide a satisfactory high-speed response, such wire printing heads normally include a spring biasing mechanism. This type of printing head generally includes a printing head having an armature, a printing wire, a leaf spring, a permanent magnet, a core, a coil winding, and a stylus having a free end. The armature is provided with a length of wire (i.e. a stylus) fixed thereto and is swingably supported by the leaf spring which provides bias thereto. The permanent magnet attracts the armature toward the core against the bias of the leaf spring. In a printing operation, the coil winding disposed around the core is excited to produce a magnetic flux in a direction opposite to one associated with the permanent magnet so as to cancel the magnetic flux of the permanent magnet. The armature is thus released from the magnetic force of the permanent magnet so as to cause the free end of the stylus to hit a platen. As shown in FIG. 5, the stylus 2 is connected at an end 21 thereof to an end portion of the armature 18 which is thinner than the opposite end portion of the armature. The printing wire is bonded or brazed on the extreme end of end portion 19a.
However, a recent improvement in the printing speed tends to increase a load imposed on the brazed connection between the armature and the stylus. In order to obtain higher printing speeds, the armature must be of a reduced weight. This generally requires that the area of the brazed connection be decreased.
With the armature of the conventional wire printing head, the printing wire is simply fixed to the end of the armature. Consequently, it is difficult to obtain a sufficient bonding strength between the armature and the stylus. Thus, during operation of the printing head in which the printing impact is repeatedly exerted, the printing wire may become separated from the armature.